{ lib, inputs, ... }:
let
  stable-pkgs = inputs.nixos-stable.legacyPackages.x86_64-linux;
  unstable-pkgs = inputs.nixos-unstable.legacyPackages.x86_64-linux;
  inherit (unstable-pkgs.haskell.lib.compose) overrideCabal;
  includePatterns = [ ".hs" ".cabal" "LICENSE" "default.nix" "CHANGELOG.md" ];
  cleanCabalPackage = source:
    { extraPatterns ? [ ], overrides ? _: { }, }:
    hpkgs:
    let
      cleanSource =
        lib.sourceFilesBySuffices source (includePatterns ++ extraPatterns);
    in lib.pipe { } [
      (hpkgs.callPackage source)
      (overrideCabal (old:
        {
          src = cleanSource;
          preConfigure = ''
            echo "Checking that default.nix is up-to-date …"
            ${lib.getExe hpkgs.cabal2nix} . > fresh-default.nix
            cp ${cleanSource}/default.nix .
            chmod u+w default.nix
            ${lib.getExe unstable-pkgs.nixfmt} fresh-default.nix default.nix
            ${stable-pkgs.diffutils}/bin/diff -w default.nix fresh-default.nix
            echo "default.nix confirmed to be up-to-date."
          '';
        } // overrides old))
      hpkgs.buildFromCabalSdist
    ];
  haskellPackagesOverlay = final: _prev:
    lib.mapAttrs (_: package: package final) myHaskellPackages // {
      streamly = final.streamly_0_9_0;
    };
  selectHaskellPackages = attrs:
    lib.mapAttrs (name: _: attrs.${name}) myHaskellPackages;
  myHaskellPackages = {
    wizards-dialog = cleanCabalPackage ./wizards-dialog { };
    rssfeeds = cleanCabalPackage ./rssfeeds { };
    kassandra = cleanCabalPackage ./kassandra/kassandra {
      overrides = _: { doHaddock = false; };
    };
    kassandra-standalone = cleanCabalPackage ./kassandra/standalone { };
    nixpkgs-bot = cleanCabalPackage ./nixpkgs-bot { };
    builders-configurator = cleanCabalPackage ./builders-configurator { };
    status-script = cleanCabalPackage ./status-script {
      overrides = _: {
        buildDepends = builtins.attrValues {
          inherit (stable-pkgs) git khal playerctl notmuch jq tailscale;
          inherit (unstable-pkgs) nix nix-diff;
        };
      };
    };
  };
  hpkgs = unstable-pkgs.haskellPackages.override {
    overrides = haskellPackagesOverlay;
  };
  packages = selectHaskellPackages hpkgs;
in {
  flake = {
    lib = { inherit selectHaskellPackages; };
    overlays = { inherit haskellPackagesOverlay; };
  };
  perSystem = { inherit packages; };
}